The subject matter of the present disclosure relates to lighting and lighting devices and, more particularly, to embodiments of a lighting device (e.g., fluorescent lamps) that utilize a multi-layer barrier coating to reduce depletion of mercury.
Fluorescent lamps use an electric discharge to excite mercury vapor and cause a material to luminesce and emit visible light. Unfortunately, mercury often reacts with the luminescing material and with the lamp structure, e.g., the glass tube that houses the mercury vapor. These reactions deplete the quantity of mercury. Fluorescent lamps that use lower levels of mercury (e.g., less than about 3 mg/lamp in 1200 mm (e.g., 48 inches) linear fluorescent lamp) are more susceptible to mercury depletion. These lamps are becoming more common because the lower levels of mercury are more environmentally friendly and, accordingly, more attractive to consumers.
To reduce the rate that mercury depletes, some fluorescent lamps provide a chemically inert barrier that prevents reaction of the mercury and the glass tube. Changes in materials, designs, and manufacturing may, however, adversely affect features of the fluorescent lamp. For example, although certain compositions of the barrier may prevent mercury absorption, the resulting lamp does not have the aesthetic appeal because the barrier does not provide a level of opacity that appeals to consumers.